<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="../vue.js"></script>
</head>

<body>
    <div id="app">
        <input type="text" v-model="msg" />
        <button @click="count++">累加count</button>
        doubleCount:{{doubleCount}}
    </div>
    <script>
        Vue.config.productionTip = false;

        const vm = new Vue({
            el: "#app",
            data() {
                return {
                    msg: "",
                    count: 2,
                };
            },
            computed: {
                doubleCount() {
                    return this.count * 2
                },
            },
            watch:{
                msg(newVal,oldVal){
                    console.log("发送请求",newVal,oldVal);
                },
                doubleCount(){
                    console.log("重新计算了count");
                }
            }
        })
    </script>
</body>

</html>